The invention relates to a device for transporting a sheet for a sheet-processing machine, particularly a rotary printing machine, in a processing direction, the transporting device having first grippers for gripping the sheet at a leading gripper edge, as viewed in the direction of processing, the first grippers revolving in a first direction during operation; a cylinder bearing the first grippers, the cylinder having a support surface formed at the circumference thereof for supporting the sheet gripped by the first grippers; second grippers for taking over the leading gripper edge of the respective sheet from the first grippers, the second grippers revolving in a second direction opposite to the first direction; and at least one pair of sheet supports rotating about a rotational axis and formed with a pitch surface disposed concentric with the rotational axis, the pitch surface having an extent along the rotational axis less than the width of a respective nonprinted lateral margin of the respective sheet, and serving to press the sheet against the support surface within a respective lateral margin in regions of common normals of the support surface and the pitch surfaces. The invention also relates to a sheet-fed printing machine, particularly a rotary printing machine, that is equipped with the sheet-transporting device.
A device of the aforedescribed type has been disclosed heretofore by the published Japanese Patent Document JP SHO 55-18194 Y2, in accordance with which it is used to transfer a printed sheet from a printing unit to a delivery, including a continuous conveyor with grippers disposed at revolving gripper bars, by which a leading gripper edge of the sheet is grippable, the sheet, after leaving the impression cylinder, being further conveyable by the trailing edge thereof at its own resources. However, all that is achieved by this method is that the sheet is positively guided at the nonprinted side margins thereof until the trailing edge thereof passes the regions of the common normals of the cylinder surfaces and the support surface of the impression cylinder.
In order to guide the sheet farther along the path thereof to a stacking or pile station without causing smearing, it has become known heretofore, particularly, to provide sheet guide surfaces and to create flow relations between those sheet guide surfaces, on the one hand, and the respective sheet, on the other hand, which has been withdrawn therefrom, that keep the sheet at a given floating height above the sheet guide surfaces.
Alternatively, it has also been proposed heretofore in the prior art that the sheets, after exiting from a printing unit, be guided on a path to a stacking or pile station by leading edge grippers and trailing edge grippers revolving out of phase relative to one another (note the published German Patent Document DE 42 18 421 A1). To realize this, however, it is necessary that a trailing gripper margin of the sheet be gripped securely by the trailing edge grippers. But the published German Patent Document DE 42 18 421 A1 does not disclose any way of satisfying this requirement.
German Patent 627 851 offers a proposal for realizing the grasping or gripping of the trailing gripper margin by trailing edge grippers. According to this proposal, the sheet is transferred from an impression cylinder by leading edge grippers and is drawn by a first chain drive including the leading edge grippers over guide rails extending along the bottom strands of the first chain drive, namely the strands which pull the sheet, beneath these strands. Beneath these strands a second chain drive is disposed having upper strands which move in the same direction as the lower strands of the first chain drive. The second chain drive bears trailing edge grippers, which grasp the trailing gripper margin when this margin of the sheet which is supported on the guide rails reaches a location at which the upper strands of the second chain drive leave a diverting wheel or guide roller that is situated upline relative to the direction of motion of these upper strands. The trailing gripper margin of the sheet is blocked from dropping below a prescribed level by the guide rails; there is no assurance, however, that the gripper margin will not make a flapping or whipping movement after running onto the guide rails. Besides the foregoing, this construction is suitable only for first-form or single-side printing, and then only if any marks which may occur on the nonprinted side of the sheet due to a rubbing thereof across the guide rails be taken into consideration, which is highly doubtful, particularly when the obverse or reverse side of the sheet is subsequently printed in a later pass or run.
It is accordingly an object of the invention to provide a device for transporting a printed sheet for a rotary printing machine without smearing, the transporting device being produced without having to resort to the use of stationary guiding devices.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a device for transporting a sheet for a sheet-processing machine in a processing direction, comprising first grippers for gripping the sheet at a leading gripper edge, as viewed in the direction of processing, the first grippers revolving in a first direction during operation; a cylinder bearing the first grippers, the cylinder having a support surface formed at the circumference thereof for supporting the sheet gripped by the first grippers; second grippers for taking over the leading gripper edge of the respective sheet from the first grippers, the second grippers revolving in a second direction opposite to the first direction; and at least one pair of sheet supports rotating about a rotational axis and formed with a pitch surface disposed concentric with the rotational axis, the pitch surface having an extent along the rotational axis less than the width of a respective nonprinted lateral margin of the respective sheet, and serving to press the sheet against the support surface within a respective lateral margin in regions of common normals of the support surface and the pitch surfaces; and suction grippers revolvable in the second direction and for taking over from the cylinder a trailing gripper margin of the sheet which has been placed on the support surface of the cylinder by the sheet supports.
In accordance with another feature of the invention, the transport device includes a sheet guiding drum comprising the second grippers, the sheet supports and the suction grippers.
In accordance with a further feature of the invention, the transport device includes a transfer drum connected in series with the sheet guiding drum and operationally rotating in the first direction, the transfer drum having third grippers for taking over the leading gripper margin from the second grippers, and having suckers following the third grippers for taking over the trailing gripper margin from the suction grippers; and an operationally revolving continuous conveyor including pregrippers and post-grippers, whereof the pregrippers are for taking over the leading gripper margin from the third grippers, and the post-grippers are for taking over the trailing gripper margin from the suckers.
In accordance with an added feature of the invention, the transport device includes an operationally revolving continuous conveyor comprising the second grippers, for taking over the leading gripper margin of the respective sheet from the first grippers, and trailing edge grippers for taking over the trailing gripper margin of the respective sheet from the suction grippers.
In accordance with an additional feature of the invention, the trailing edge grippers grasp the trailing gripper margin in an outlet wedge of a nip formed between the support surface and the pitch surfaces.
In accordance with yet another feature of the invention, the sheet supports have an adjustable mutual spacing.
In accordance with yet a further feature of the invention, the pitch surfaces have an adjustable circumferential extent.
In accordance with yet an added feature of the invention, the suction grippers have an adjustable phase position.
In accordance with yet an additional feature of the invention, the suckers have an adjustable phase position.
In accordance with another aspect of the invention, there is provided a sheet-processing machine including a device for transporting a sheet in a processing direction, the sheet-transporting device comprising first grippers for gripping the sheet at a leading gripper edge, as viewed in the direction of processing, the first grippers revolving in a first direction during operation; a cylinder bearing the first grippers, the cylinder having a support surface formed at the circumference thereof for supporting the sheet gripped by the first grippers; second grippers for taking over the leading gripper edge of the respective sheet from the first grippers, the second grippers revolving in a second direction opposite to the first direction; and at least one pair of sheet supports rotating about a rotational axis and formed with a pitch surface disposed concentric with the rotational axis, the pitch surface having an extent along the rotational axis less than the width of a respective nonprinted lateral margin of the respective sheet, and serving to press the sheet against the support surface within a respective lateral margin in regions of common normals of the support surface and the pitch surfaces; and suction grippers revolvable in the second direction and for taking over from the cylinder a trailing gripper margin of the sheet which has been placed on the support surface of the cylinder by the sheet supports.
In accordance with a further aspect of the invention, there is provided a rotary printing machine including a device for transporting a sheet in a processing direction, the sheet-transporting device comprising first grippers for gripping the sheet at a leading gripper edge, as viewed in the direction of processing, the first grippers revolving in a first direction during operation; a cylinder bearing the first grippers, the cylinder having a support surface formed at the circumference thereof for supporting the sheet gripped by the first grippers; second grippers for taking over the leading gripper edge of the respective sheet from the first grippers, the second grippers revolving in a second direction opposite to the first direction; and at least one pair of sheet supports rotating about a rotational axis and formed with a pitch surface disposed concentric with the rotational axis, the pitch surface having an extent along the rotational axis less than the width of a respective nonprinted lateral margin of the respective sheet, and serving to press the sheet against the support surface within a respective lateral margin in regions of common normals of the support surface and the pitch surfaces; and suction grippers revolvable in the second direction and for taking over from the cylinder a trailing gripper margin of the sheet which has been placed on the support surface of the cylinder by the sheet supports.
To achieve the objects of the invention, the transporting device is equipped with suction grippers which revolve during operation in the second direction, the suction grippers taking up from the cylinder a trailing gripper margin of the respective sheet, which has been placed on the support surface of the cylinder by the sheet supports.
With this transporting device, the sheet that has been grasped by the second grippers is first peeled from the support surface of the cylinder that bears the first grippers, the respective peeled-off portion of the sheet extending from the second grippers to the common normals of the support surface and the pitch surfaces. The second grippers travel along an arc-shaped path after passing the common normals. The side margins of the portion of the sheet that has been peeled from the support surface, which represent nonprinted zones, are thus wound onto the pitch surfaces of the sheet supports. The bending forces which this exerts upon the sheet by way of the first gripper give rise to opposing reactive forces of the sheet, which bias or prestress the portions of the yet unwound sheet towards the support surface of the cylinder. The invention exploits this effect, which causes these reactive forces to press a trailing gripper margin of the sheet against the support surface as well, so that this gripper margin is placed on the support surface orthogonally when passing the common normals and is therefore available for a defined grasping by the gripping mechanisms, which are realized as suction grippers, in view of the support surface of the cylinder, which forms a closed surface. After the trailing gripper margin has been successfully accepted by the suction grippers, the sheet is stable on all of the margins thereof; it is thus accessible for secure grasping by mechanically opening and closing grippers particularly at the trailing gripper margin, and it is possible to transport the sheet further under positive guidance of both the leading and trailing gripper margins thereof.
In a preferred development, a sheet guiding drum is provided which comprises the second grippers, the sheet supports, and the suction grippers.
In a preferred application thereof, in the case of a serially constructed rotary printer, such a sheet guiding drum serves to transport the sheet from one processing station, for example, a printing unit, to the next processing station, for example, an additional printing unit or a varnishing unit, and so on, and it spares sheet guiding mechanisms (which are typically pneumatic) that are needed between the processing stations in conventional sheet transferring devices.
A further development provides for a transfer drum to be connected in series with the sheet guiding drum and to rotate in the first direction during operation, the transfer drum having third grippers which take over the leading gripper margin from the second grippers, and having suckers following the third grippers, which take over the trailing gripper margin from the suction grippers; and by continuous conveyors comprising operationally revolving pregrippers and post-grippers, of which the pregrippers take over the leading gripper margin from the third grippers, and the post-grippers take over the trailing gripper margin from the suckers.
In a preferred development of the transfer drum, it comprises sheet supports in the same manner as the sheet guiding drum, the sheet supports having pitch surfaces which are concentric with the rotational axis of the transfer drum and which press the sheet against the sheet guiding drum within the side margins of the sheet exclusively, namely in regions of common normals of the pitch surfaces of the sheet guiding drum, on the one hand, and of the transfer drum, on the other hand.
In another development, which is specifically suitable for guiding sheets for one-sided or first-form printing or in a second pass through the rotary printing machine, the transfer drum has a plurality of pitch surfaces concentric with the rotational axis thereof, which follow one another in the axial direction of the transfer drum, with intervening spaces. The intervening spaces are dimensioned to accommodate the suckers and, in a preferred development, to allow the post-grippers to drop into the same intervening space wherein a sucker is disposed.
With the continuous conveyor, the sheet can then be transported by positively guiding the leading and trailing gripper margins thereof, namely in a direction towards a stacking or pile station of the rotary printing machine, without requiring conventional guiding devices for smear-free sheet guidance.
In another development, the aforedescribed transporting device constructed in accordance with the invention, namely, with suction grippers which revolve, during operation, in the second direction and which take over from the cylinder a trailing gripper margin of the sheet that has been placed onto the support surface of the cylinder by the sheet supports, comprises a continuous conveyor which revolves during operation, including the second grippers which are provided for taking over the leading gripper margin from the first grippers, as well as, trailing edge grippers which take over the trailing gripper margin from the suction grippers.
The continuous conveyor herein provided can be used in the aforedescribed manner for transporting the sheet in a direction towards a stacking or pile station and can be arranged for this purpose directly downline from the cylinder bearing the first grippers, this cylinder having a support surface for supporting the sheet holohedrally, as is the case with an impression cylinder, in particular.
In a preferred development of the continuous conveyor that immediately follows the cylinder, the trailing edge grippers thereof grasp the trailing gripper margin in the outlet wedge of the gap formed between the support surface and the pitch surfaces. This makes possible measures by which the trailing edge grippers of the continuous conveyor can pass through the regions of common normals of the support surface of the cylinder and the pitch surfaces of the sheet supports without colliding. It is common to the measures provided for this purpose that the trailing edge grippers pass the cylinder inside an envelope that can be placed about the revolving suction grippers.
In another preferred development, provision is made for the mutual spacing between the sheet supports to be adjustable so as to make it possible to process sheets with different widths relative to the processing direction.
Another preferred development provides for the circumferential extent of the pitch surfaces to be adjustable. Also provided for is that the phasing or phase position of the suction grippers and of the suckers be adjustable.
These measures make possible the processing of sheets with different lengths relative to the processing direction.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for transporting a sheet for a rotary printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: